Jamaica's Usain Bolt on his way to victory in his 100m heat at the Olympic Stadium. Photograph: Mark J Terrill/AP

Usain Bolt has eased through the opening round of the 100m ahead of Sunday's much anticipated final, but suffered a minor scare when he stumbled out of the blocks.

The reigning Olympic champion won his heat in 10.09sec but had a slow start after appearing to stumble, before recovering to ease through and allay fears about his health. The Antiguan Daniel Bailey came second in 10.12.

The Jamaican world record holder has predicted that the 100m final will be one of the most keenly contested races in history, with the whole field potentially capable of going under 10 seconds.

Anticipation has been heightened further by the fast times already posted on the Olympic Stadium track, with the American Ryan Bailey running 9.88 shortly before Bolt appeared to huge cheers.

On the big screens before the heats the crowd had watched highlights of historic moments from the blue-riband event, as if they needed to be hyped up any more. They included, of course, Bolt's searing 9.69 run in Beijing.

Bolt's friend and rival Asafa Powell won his heat in 10.04, ahead of Britain's teenage sprint hopeful Adam Gemili, who finished second in 10.11.

There had been ongoing murmurs about Bolt's fitness, despite the fact he had done his best to quash them at a press conference last week.

Ahead of his heat, which he ran in lane seven, Bolt got a predictably rousing reception. But that afforded the British hopeful James Dasaolu was almost as loud. And he made the most of the home support to also qualify for the semi-finals in a season's best time of 10.13.

Dwain Chambers posted a season's best of 10.02 to win his heat as the quickest of the three Britons.

Much has already been made of the speed of the Mondo surface, after a succession of women ran under 11 seconds in their heats on the first day of competition.

The American Tyson Gay, the second fastest man in history, won his heat in 10.08. His compatriot Justin Gatlin, who served a four-year doping ban in 2007, ran the fastest time in a 100m heat in Olympic history with 9.97. But in the very next heat, Bailey ran 9.88 – equalling his lifetime best.

Yohan Blake, the third Jamaican likely to reach the final, also won his heat – in 10 seconds dead.

Following the introduction of a preliminary round to weed out some of the slower runners, there are now three main rounds rather than four in the 100m. Hence, sprinters are expected to run harder from the start.